In Diameter networks, sessions are often established between policy and charging rules functions (PCRFs) and other nodes. For example, PCRFs establish Sy sessions with online charging systems (OCSs) to monitor policy counters, which govern subscriber spending limits with regard to one or more services. The PCRF makes policy decisions based on the status of the policy counters received from the OCS. On the Rx interface, the PCRF sends re-authorization request (RAR) messages to application functions (AFs) to re-establish sessions with the application functions.
The PCRF reserves memory and other resources associated with each session on each interface that the PCRF supports. If a session is terminated by the OCS or AF, the PCRF may not be aware of the termination. A session that is terminated by the remote end but where the PCRF is not aware of the termination is referred to herein as an orphan session. As the number of sessions managed by the PCRF increases, wasted resources due to orphan sessions can degrade PCRF performance.
The Sy and Rx interface specifications to not define procedures for detecting orphan sessions. One possible procedure for detecting orphan sessions could be to use an existing message on one of the interfaces to audit sessions. However, if an existing message is used to audit sessions, that message can trigger undesirable results, such as a subscription to future updates. For example, on the Sy interface, if a spending limit request with a valid policy counter identifier is used as an audit message, sending such a message to the OCS will result the PCRF receiving policy counter updates for the session. An audit procedure that triggers a subscription and future updates is undesirable as such a procedure further wastes PCRF and OCS resources. The base Diameter protocol includes keepalive timers and related procedures for Diameter messages. However, such procedures only test the availability or unavailability of Diameter communications, which could represent hundreds or thousands of sessions and is thus unsuitable for detecting individual orphan sessions.
Accordingly, there exists a need for methods, systems, and computer readable media for detecting orphan Sy or Rx sessions using audit messages with fake parameters